Reed relays are well-known electrical devices that are generally used in applications where fast operating times, reliability, and sensitivity are required. Typical applications include data processing, communications and computer equipment, logic circuitry and other types of sophisticated control circuits.
FIG. 1 illustrates one type of a typical existing reed relay called a dry reed relay 1. The dry reed relay 1 uses dry reed switches 10 consisting of long, thin contact blades 12, 14 hermetically sealed in a glass capsule 16 with terminations 18, 20 extending from respective ends of the capsule 16a, 16b. The reed switches 10 are sealed inside the glass capsule 16 in an atmosphere of dry inert gas. The encapsulation seals out contaminates and extends the useful life of the contact blades 12, 14. The relay 1 also has an operating coil 22 that is wound on a bobbin 24 that has cavities 24a within which a number of the glass capsules 16 are inserted. This creates a coil-switch assembly. The terminations 18, 20 of the reed switches 10 are connected to terminal pins 26, 28 which extend from the assembly, for example, as printed circuit board terminals. The entire assembly is contained within an enclosure 30 with the terminal pins 26, 28 extending from the enclosure 30.
Another type of reed relay is a mercury-wetted contact reed relay. This type of reed relay has a glass capsule that contains fixed contacts, a long thin movable armature blade located between the fixed contacts, and a small reservoir of mercury. The capsule is hermetically sealed, for example, in a high pressure hydrogen atmosphere. The use of mercury insures continual renewal of contact material, constant contact characteristics and permanent low contact resistance. The mercury also provides for an absence of contact bounce and makes for positive contact closure. The relay also has an operating coil that is wound on a bobbin that has cavities within which a number of the glass capsules are inserted. The terminations of the fixed contacts and the armature are connected to terminal pins which extend from the assembly. The entire assembly is contained within an enclosure with the terminal pins extending from the enclosure.
A limitation of the existing dry reed relay is the risk of contact separation during contact switching (i.e., contact bounce or chatter) and during vibrations and other disturbances of the relay operation. This has an impact on reliability and sensitivity and, thus, degrades relay performance. The only alternative is the use of more expensive and more complicated mercury-wetted contact reed relays. In certain applications, however, mercury-wetted contact reed relays may not be suitable. Consequently, a dry reed relay with a reduced contact separation characteristic is desirable.